Comparison of priming versus slow injection for reducing etomidate-induced myoclonus: a randomized controlled study

BACKGROUND: Etomidate injection is often associated with myoclonus. Etomidate injection technique influences the incidence of myoclonus. This study was designed to clarify which of the two injection techniques—slow injection or priming with etomidate—is more effective in reducing myoclonus. METHODS: This prospective randomized controlled study was conducted on 189 surgical patients allocated to three study groups. Control group (Group C, n = 63) received 0.3 mg/kg etomidate (induction dose) over 20 s. Priming group (Group P, n = 63) received pretreatment with 0.03 mg/kg etomidate, followed after 1 min by an etomidate induction dose over 20 s. Slow injection group (Group S, n = 63) received etomidate (2 mg/ml) induction dose over 2 min. The patients were observed for occurrence and severity of myoclonus for 3 min from the start of injection of the induction dose. RESULTS: The incidence of myoclonus in Group P (38/63 [60.3%], 95% CI: 48.0–71.5) was significantly lower than in Group C (53/63 [84.1%], 95% CI: 72.9–91.3, P = 0.003) and Group S (49/63 [77.8%], 95% CI: 66.0–86.4, P = 0.034). Myoclonus of moderate or severe grade occurred in significantly more patients in Group C (68.3%) than in Group P (36.5%, P < 0.001) and Group S (50.8%, P = 0.046), but the difference between Groups P and S was not significant (P = 0.106). CONCLUSIONS: Priming is more effective than slow injection in reducing the incidence of myoclonus, but their effects on the severity of myoclonus are comparable.